Bernal was still good enough to finish within 10-15 seconds of the 'bigs' yesterday. Withdrawing him will be precautionary, if it was too bad he would have let go and given Sivakov free reign earlier. No point in continuing to race in a prep race and making yourself worse in this truncated and compressed calendar.
Yes, it limits how much preparation time he has but how many people with serious designs on the Tour are going to race that much after this weekend until the Grand Départ? Bernal just has to not get worse, and survive through the early stages in enough contention that he can be able to claw that time back, and he's capable of doing that. He won't lose much time in Nice, nobody's going to be going from long range on the Col de Turini on stage 2, and he's capable of holding on on the Col d'Èze in current form even if he doesn't improve, maybe somebody can best him wiith explosivity on Quatre Chemins, but he won't lose a huge amount there. There really isn't scope to lose too much to Orcières-Merlette with a reasonable train to protect him and I can't imagine Ineos disintegrating on such a stage with little real challenge before the MTF. If he doesn't worsen between now and the Grand Départ then realistically by the time we get to the Pyrenées he ought to be back in a reasonable level of form and the Pyrenean stages are ones that don't lend themselves to huge gaps - the bunch knows Peyresourde like the back of its hand and Marie-Blanque will be the realistic only attacking platform in that stage, so it's really just Col de la Lusette he has to be concerned about.